Bug juice

摘要

The gastrointestinal tract involves a miraculous complex ecosystem composed of countless bacteria in homeostasis with the host immune system. Although far greater numbers of microbial cells than host cells normally reside in the gut, adverse immunity does not usually occur. Colonization of the newborn intestine with foreign organisms is essential for fundamental processes such as the development of the local and systemic immune system. However, the bacterial molecules mediating this symbiotic partnership have not yet been uncovered. Now, a glimpse into the molecular mechanisms involved has been revealed. Colonization of germ-free mice with a single ubiquitous gut microorganism, Bacteroides fragilis, is shown to be sufficient for the development of the peripheral immune system (including systemic T-cell development and lymphoid organogenesis, which is normally devoid in germ-free mice).